Delta4, 5-3, 11-diketo-20, 21-dioxy-pregnenes and process



V wherein R is hydrogen or acyl.

Patented June 13, 1950 UNITED STATES PATENT OFFICE A -3,11-DIKETO-20,21-DIXY-PREGNENES AND PROCESS Lewis H. Sarett, Princeton, N. 3., assignor to Merck & 00., Inc., Railway, N. J a corporation of New Jersey No Drawing. Application August 2, 1946, Serial No. 687,981

9 Claims. 1

This invention is concerned generally with novel chemical compounds of the cyclopentanodimethylpolyhydrophenanthrene series and to processes of preparing the same; more particularly it relates to stereoisomers of A -3,11-diketo-20,2ldihydroxy-pregnene and acylated derivatives thereof, and with processes for converting these stereoisomers to esters of dehydrocorticosterone;

it is further concerned with methods of manufacturing these compounds from readily available starting materials. Dehydrocorticosterone esters are synthetically formed derivatives of physiologically occurring and active hormones of the adrena1 cortex and are useful in the treatment of Addisons disease and similar maladies. It is likewise useful in treating trauma, resulting from an inadequacy of the adrenal gland.

These stereoisomeric A -3,11-diketo-29,2l-di hydroxy-pregnenes and their acylated derivatives, subject of this application, can be represented by the following structual formulae:

This formula, for

purposes of convenience is hereinafter reproduced below in the abbreviated form:

CHgO R CHzOR --H H--COR H: OH; H!

C C O O wherein R has the significance above defined.

In the following description of the invention, the stereochemical relationships of the substituents are indicated by the following conventions:

1. A substituent at the C20 position is arbitrarily designated as a or 5 depending upon the stereochemical configuration thereof; in this application, the convention is adopted that the {3 configuration is represented by writing the C20 substituent (hydroxyl or acyloxy) to the right of the C20 carbon side chain thus:

OHaOH H- I ---OH and in the case of the epimeric a configuration, the substituent is written to the left of the side chain, thus:

CHaOH 2. The stereochemical relationship of rings A and B is indicated in the formulae by a solid line representing the valence bond in the cis configuration.

In accordance with the present invcntion, it is now found that stereoisomers of A -3,l1-diketo- 20,21-dihydroxy-pregnene and their acylated derivatives can be synthesized and that these compounds can in turn be converted to dehydrocorti- CHaOR CHzOR RO- H C Ha Hz Partial 1 Partial Acylation Acylation OHzO R The starting material exists in two-epimeric forms, namely the. 4-bromol-3,11 -diketo-20-(a)- 21-diacyloxy pregnane (l), and 4-bromo-3,11-

diketo-20-(p) 21-diacyloxy pregnane (2) These:

stereoisomers and mixtures thereof are hereinafter referred to in this application by the generic expression, 4-bromo-3,11-diketo-20,21-diacyloxy pregnane, except Where it is desired to recite a specific isomer. Compounds of this class can be synthesized from the readily available desoxycholic acid and derivatives thereof asdescribed in my co-pending applications, Serial No. 649,7 60, filed February 23, 1945 (which isacontinuation-inpart of application Serial No. 605194, filedJuly 14, 1945, now abandoned); Serial No. 687,982.

(Case 1 722)/, filed' August 2, 1946', now Patent No. 2,505,838; Serial No. 687,980 (Case-1580-)", filed August 2, 1945; and Serial No. 687,983 (Case 1723) filed Aug. 2, 1946. They are convertedrto A -3,l1--

diketo-20,2l-dihydroxy-pregnene and thence to estersof dehydrocorticosterone, as indicated above by reacting said 4-bromo-3,11-diketo-20,2l-diacyloxy-pregnanes (1 & 2) with a compound capable of removing the elements of hydrogen bromide, thereby producing the A -3,1l-diketo-20,21-diacyloxy-pregnene (3 & 4) which is hydrolyzed to the corresponding dihydroxy derivative (5 & 6); partial acylation of A -3,11-diketo-20,21-dihydroxy-pregnene (5 & 6) produces the 21-monoacyl derivative ('7 & 8) which upon oxidation, yieldsan ester of dehydrocorticosterone (9).

In accordance with the present invention, a stereoisomer of 4-bromo-3,l1-diketo-20,2ldiacyloxy-pregnane, as for example, l-bromo- 3,11-diketo-20-(w) 21 diacetoxy pregnane; 4-bromo-3,11-diketo-20 (,8) 21 diacetoxypregnane; 4bromo-3,11-diketo-2O (,6) 21- dipropionoxy-pregnane; 4-bromo-3,l1-diketo-20- (mi-21 dibutyroxy pregnane; 4 bromo 3,11-

.diketo-2o-(m-2l-dibenzoxy pregnane; or mixtures thereof, is treated with a reagent capable of removing the elements of hydrogen bromide such as a tertiary amine, as for example, pyridine, picoline, quinoline and the like, thus causing the formation of a double bond in the desired 4,5- position. In the preferred process the crude 4- bromo 3,l'1-diketo-20,2l-diacyloxy pregnane is reacted directly, as for example by refluxing, with pyridine to produce the desired A -3,11- diketo 20,21 diacyloxy pregnene, having the structural formula:

CHQGR HOB CH1 C.

wherein R is acyl. This last mentioned product can be hydrolyzed by any convenient method, as for example, by reaction with an aqueous solution containing a mineral acid or an alkaline agent, whereby A -3,11-diketo-20,21-dihydroxypregnene is obtained having the structural formula:

CHIOH JHOH corresponding A -3,11-diketo 20 hydroxy-21- acyloxy-pregnene having the structural formula:

CHnOR HOH CH: H5

wherein R is acyl. Among the acylating agents which are useful for this purpose are aliphatic anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, and the like, organic acyl halides such as acetyl chloride, propionyl chloride, butyryl choride, benzoyl chloride, and the like. If desired, the corresponding acid may be substituted in whole or part for the anhydride used, but the anhydride is preferred. In effecting this partial acylation, it is important not to use an amount of acylating agent greatly in excess of an equi molecular proportion, as otherwise, the yields of monoacylated compound is decreased because of formation of the undesired diacyl compound. The monoacylated compound is separated from the acylation mixture by any convenient procedure, as for example, by chromatographic absorption using activated alumina.

M -3,1l-diketo-ZO-hydroxy 21-acyloxy-pregnene, which can be either the 20-(a) or 20-(6) stereoisomer or mixtures thereof, is then reacted with an oxidizing agent such as chromic acid, preferably in solution in an inert solvent, such as an aqueous aliphatic acid, as for example, aqueous acetic acid, aqueous propionic acid, and the like. It is preferred to conduct the reaction at about 20 C., under which conditions the time required for the oxidation is approximately 1 hour, but higher or lower temperatures may be employed if desired. Independent of the stereoisomeric configuration of the hydroxyl group on the ZO-carbon atom, the identical product is obtained by the oxidation, namely, M -3,11,26- triketo- ZI-acyloXy-pregnene, since in this compound the 20 carbon atom is no longer asymmetric. This product, commonly referred to as an ester of dehydrocorticosterone, can be represented by the following structural formula:

CHQOR wherein R is an acyl group. The product, which crystallizes directly from the reaction mixture upon addition of water, is readily recovered by filtration, and can be purified recrystallization.

In practicing the present invention, the oxidation is preferably carried out under mild conditions in a medium having a pH of approximately 1 to 7; although the preferred medium is a lower aliphatic monocarboxylic acid, it is possible to added thereto.

employ dialkyl ketones, such as acetone, as a medium for the oxidation reaction.

The following examples illustrate methods of carrying out the present invention, but it is to be understood that these examples are given by way of illustration and not of limitation.

Example 1 About 790 mg. of 4-bromo-3,11-diketo-20-( S) Zl-acetoxy-pregnane is dissolved in about 30 cc. of pyridine and the solution refluxed for approximately 10 hours. The pyridine is then evaporated under reduced pressure, the residue is dissolved in chloroform and the chloroform extract washed with dilute hydrochloric acid, then with dilute aqueous sodium bicarbonate solution and finally with water. The resulting chloroform solution is then evaporated to dryness under reduced pressure and the residue (about 590 mg.) is dissolved in about 3 :cc. benzene and about 30 cc. of ether is added to this solution, the flocculent precipitate which forms is-filtered ofif and the filtrate evaporated on the steam bath until :crystals separate; petroleum ether is added carefully to complete the crystallization. The product so obtained is purified by repeated recrystallization from methanol and finally from acetone to produce substantially pure Ad -3,11- diketo-ZO 3) 21 diacetoxy pregnene; M. P. 207-208 C. (corn); [a] =+170 (acetone).

About 144 mg. of A -3,11-diketo-20-(c)-21- diacetoxy-pregnene is dissolved in about 7 cc. of hot methanol and a solution containing about 133 mg. of potassium carbonate and about 300 mg. of potassium bicarbonate in about 4.4 cc. of water is added thereto. The solution is allowed to stand at room temperature for approximately 16 hours, the excess alkali is neutralized by addition of about 0.3 cc. of acetic acid and the methanol is evaporated under reduced pressure. The resulting mixture is diluted with water and then extracted with chloroform. The chloroform layer is washed with Water, evaporated to dryness under reduced pressure and the residue purified by recrystallization from acetone to produce substantially pure A -3,11-diketo-20-(p)-21-dihydroxy-pregnene; M. P. 2235-2245 C. (corn); [a] =[176.

About mg. of A -3,l1-diketo20-(B) -21-dihydroxy-pregnene is dissolved in about 1 cc. of absolute dioxane and the dioxane is evaporated under reduced pressure. The dry residue is dissolved in about 0.68 cc. of absolute dioxane and a mixture containing about 66 mg. dioxane, 38 mg. acetic anhydride and 32.7 mg. of pyridine is The glycol is not entirely soluble in this mixture and the mixture is warmed gently with stirring until all of the crystals have dissolved. The solution is then allowed to stand at about 25 C. out of contact with atmospheric moisture for about 60 hours. A few cc. of water are added and evaporated under reduced pressure and the dry residue is then chromatographed over about 3 g. of activated alumina. The middle fractions are purified by recrystallization from dilute methanol to produce substantially pure A -3,l1-diketo-20 (c) hydr-oxy 21 acetoxypregnene; M. P. l61.5-162.5 C. (corn).

About 36 mg. of A -3,l1-diketo-20-(fl) -2l-diacetoxy-pregnene is dissolved in about 3.3 cc. of glacial acetic acid and a solution containing about 18 mg. of chromic acid, about 0.3 cc. of acetic acid and about 0.3 cc. of water is added thereto at a temperature of 18 C. The resulting mixture is allowed to stand at about 18 C. for approximate y 1 hounsumcien zsodium .sulfite s a e thereto to destroy'excess chromicacid and the acetic acid solution is evaporated tosmall volume under reduced pressure and water is added. The crystalline material whichprecipitates is filtered and purified by recrystallization from a small volume of methanol to produce substantially pure dehydrocorticosterone acetate; M. P. 1825-1835 C. (corn); [a] .=-|T-215 (acetone).

Example 2 About 703mg. of amorphous 4bromo-3,l1- diketo-ZO- (a) -2l-diacetoxy-pregnene is dissolved in about 30 cc. of pyridine and the solution refluxed for approximately hours. The pyridine is dissolved 'in chloroform, washed with dilute hydrochloric acid then with dilute aqueous so- .dium bicarbonate solution and, finally with water and the chloroform solution evaporated to dryness under reduced pressure. The residue is dissolved in about 3 cc. of benzene, about 30 cc. of ether is added thereto and the fiocculent precipitate which forms is removed by filtration and the filtrate evaporated to dryness. The residue is purified by recrystallization from dilute methanol to produce crude A -3,l1-diketo-20-(a) -'21-diacetoxy-pregnene; M. P. about 132-140" C.

The above compoundis best purified by saponiifying to the correspondingdihydroxyderivative and then acetylating the product. About 140 mg. of said crude A -3,11-diketo-20-(a)-2l-diacetoxy-pregnene is dissolved'in about 7 cc. of hot methanol and a'solution of about 133mg. of potassium carbonate, about 309 mg. of potassium bicarbonate and about 4.4 cc. of water is added thereto. The solution is then allowed to stand at room temperature for approximately '16 hours, the excess alkali is'neutralized by addition of approximately G.3 cc. of acetic acid and the methanol is evaporated under reduced pressure. .Water is added andthe mixture is extracted with chloroform, the chloroform layer is Washed with water and evaporated to dryness under reduced pressure. The residue is purified by recrystallization from water to produce substantially pure A -3,'l1-dL eto-20-(a) -21 dihydroxy-pregnene; M. P. 19S-196.5 0. (corn); [a] 76.5 (acetone). This dihydroxy compound is then converted'to the corresponding diacetate as follows: About of A -3,11-diketo-20-(a) -21-dihydroxy-pregnene is added to a solution containing about 0.2 cc. of pyridine and about 0.2 cc. acetic anhydride and the resulting solution is heated on the steam bath for approximately minutes. Water is added to the reaction mixture, the resulting solution evaporated .to dryness under reduced pressure, and the residue is purified by recrystallization first from dilute methanol and finally from acetone-petroleum ether to produce substantially pure A 3,11-dlk8t0-20-(-a.)-21-dl acetoxy-pregnene; M. P. 153.5-154.5 C. (corn); [a] -,.=133 (acetone).

About 60 mg. of A -3,11-diketo--(a) 21-dihydroxy-pregnene is addedto a mixture of about 66 mg. of dioxane, about 38 mg. of acetic anhydride and about 32.7 mg. of pyridine, as described in Example 1 for the -20-( 3)-isomer. In the present experiment, the -20-(a)-isomer is completely soluble at room temperature in the dioxane solution; the solution is then kept at room temperature out of contact with atmospheric moisture for approximately 60 hours, and the reaction product worked up and chromatographed as previously described for the isomeric 20-93)- .monoacetate. The crude product is purified by methanolto produce substantially pure 13 3,11-

diketo 20 (a) -,hydroxy-Zl-acetoxy-pregnene; M. P. 221-227 C. (corn) About 14 mg. of A -3,11-diketo-20-(a)-hydroxy-21-acetoxy pregnene is oxidized by the procedure employed.for oxidation of the -20-(fi) isomer as describedin Example 1, and the crude product purified by recrystallization from methanol as previously described. The product is substantially pure dehydro-corticosterone acetate, identical with the product obtained in Example 1; M. P. l82.5-l83.5 C. (corr.) mixed melting point with the product obtained in Example 1 is unchanged; [a] =+215 (acetone).

Various changes and modifications may be made in my process as described without departing from the scope of my invention. To the extent that these changes and modifications are within the purview of the annexed claims, they are to be considered as part of my invention.

I claim:

1. The process of preparing an ester of dehydrocorticosterone which comprises reacting :8. 20,21 disubstituted 4-bromo-3,11-diketo-pregnane, in which the substituents in the 20- and 2l-positions have the formulae: 3000- and RCOO-, respectively, wherein R and R are radicals selected from the class which. consists of phenyl and lower alkyl radicals. with a tertiary amine to remove the-elements of hydrogen bromide from the molecule'to form the corresponding A 3,11 diketo-20,21-diacyloxy-pregnene; hydrolyzing this compound to form the corresponding 20,21-dihydroxy derivative; and partially-acylating. this compound by reaction with an :acylating agent selected from the class which consists of benzoyl chloride, lower aliphatic carboxylic acid anhydrides and lower aliphatic carboxylic acid halides, the amount of said acylating agent employed being substantially the-theoretical quantity required'to esterify onehydroxyl group,.to produce the corresponding A -3,11-diketo-ZO-hydroxy-Zl-acyloxy-pregnane; and reacting the resulting ester with an oxidizing agent to produce an ester of dehydrocorticosterone.

2. The process of preparing dehydrocorticosterone acetate which comprises reacting -bromo- 3,11-diketo-20,21-diacetoxy-pregnane with pyridine to 'form the corresponding A -3,11-diketo- 20,2l-diacetoxy-pregnene; reacting this compound with an alcoholic solution containing an alkali metal carbonate to effect saponification of the ester groupings; partially esterifying the resulting A -3,11-diketo-20,2l-dihydroxy-pregnene by reaction with substantially the theoretical quantity of acetic anhydride to produce the corresponding A 3,11 diketo-20-hydroxy-21- acetoxy-pregnene; and reacting this compound with chromium trioxide to produce dehydrocorticosterone acetate.

3. The process which comprises reacting chromium trioxide with a 21-substituted-A -3Jldiketo-ZO-hydroxy-pregnene, in which the substituent in the 21-position has the formula RCOO-, wherein R is a radical selected from the class which consists of phenyl and lower alkyl radicals, to produce the corresponding ester .of dehydrocorticosterone.

4. The process which comprises reacting A 3,11 diketo 20 hydroxy-2l-acetoxy-pregnene with chromium trioxide to produce an ester of dehydrocorticosterone.

5. A 3,11-diketo-20-(a)-21-diacetoxy-pregnone, having a melting point of about 153.5-154.5 REFERENCES CITED C. and an [a] =+133 C. (acetone). The folio r f 6. A 3,11 -diketo-20-(a)-21-dihydroxy-pregme of gjgf i eremes are m the nene, having a melting point of about 196-196.5 C. and an [a] =+176.5 (acetone). 5 UNITED STATES PATENTS 7. 21 substituted-A 4;I-diketo-ZO-hydroxypregnenes, in which the substituent in the 21- 3 6 g Apr i position has the formula RCOO-, wherein R is a 2308833 Ruzick; 1943 lower alkyl radical.

8. A 3,11 diketo-20-(fl)-hydroxy-21-acet- 10 2322309 Lgemann June 1943 oxy-pregnene having a melting point of about FOREIGN PATENTS 161.5-162.5 C. N b t 9. 20,21 disubstituted A -3,11-diketo-preg- P er Conn ry Date nenes, m which the substituents in the 20- and 21- 8161852 France May 10, 1937 positions have the formulae RCOO- and 15 R'CO0-, respectively, wherein R and. R are lower alkyl radicals.

LEWIS H. SARETT. 

1. THE PROCESS OF PREPARING AN ESTER OF DEHYDROCORTICOSTERONE WHICH COMPRISES REACTING A 20,21 - DISUBSTITUTED - 4-BROMO-3,11-DIKETO-PREGNANE, IN WHICH THE SUBSTITUENTS IN THE 20- AND 21-POSITIONS HAVE THE FORMULAE: RCOO- AND R''COO-, RESPECTIVELY, WHEREIN R AND R'' ARE RADICALS SELECTED FROM THE CLASS WHICH CONSISTS OF PHENYL AND LOWER ALKYL RADICALS, WITH A TERTIARY AMINE TO REMOVE THE ELEMENTS OF HYDROGEN BROMIDE FROM THE MOLECULE TO FORM THE CORRESPONDING $**4,5-3,11 - DIKETO-20,21-DIACYLOXY-PREGNENE; HYDROLYZING THIS COMPOUND TO FORM THE CORRESPONDING 20,21-DIHYDROXY DERIVATIVE; AND PARTIALLY ACYLATING THIS COMPOUND BY REACTION WITH AN ACYLATING AGENT SELECTED FROM THE CLASS WHICH CONSISTS OF BENZOYL CHLORIDE, LOWER ALIPHATIC CARBOXYLIC ACID ANHYDRIDES AND LOWER ALIPHATIC CARBOXYLIC ACID HALIDES, THE AMOUNT OF SAID ACYLATING AGENT EMPLOYED BEING SUBSTANTIALLY THE THEORETICAL QUANTITY REQUIRED TO ESTERIFY ONE HYDROXYL GROUP, TO PRODUCE THE CORRESPONDING $**4,5-3,11-DIKETO-20-HYDROXY-21-ACYLOXY-PREGNANE; AND REACTING THE RESULTING ESTER WITH AN OXIDIZING AGENT TO PRODUCE AN ESTER OF DEHYDROCORTICOSTERONE. 